1. Field of the Invention
The present invention relates to signal processing techniques. More particularly, the present invention relates to methods for processing audio signals.
2. Description of the Related Art
The majority of the stereo spreader designs implemented today use a so called stereo shuffling topology that splits an incoming stereo signal into its mid (M=L+R) and side (S=L−R) components and then processes those S and M signals with complementary low and highpass filters. The cutoff frequencies of these low and high-pass filters are generally tuned by ear. The resultant S′ and M′ signals are recombined such that 2L=M+S and 2R=M−S. Unfortunately, the end result usually yields a soundfield that is beyond the physical loudspeaker arc but is not precisely localized in space. What is desired is an improved stereo spreading method.
The M-S matrix can have other novel applications to spatial audio beyond the stereo spreader.
It is often desirable to reproduce binaural material over loudspeakers. In general, the aim of a crosstalk canceller is to cancel out the contra-lateral transmission path Hc such that the signal from the left speaker is heard at the left eardrum only and the signal from the right speaker is heard at the right eardrum only.
Traditional feedback crosstalk canceller designs require that the interaural transfer function (ITF) be constrained to be less than 1.0 for all frequencies. Tuning the spectral response of a traditional recursive crosstalk canceller filter design in order to control the perceived timbre is difficult or impractical. It is desirable to provide an improved crosstalk cancellation circuit that can allow tuning of the timbre of the canceller output without seriously affecting the spatial characteristics. Further it would be desirable to avoid possible sources of instability or signal clipping.